The present application relates to devices and methods and for use in percutaneous interventional surgery. In particular, the present application relates to devices and methods for providing or maintaining fluid flow through passages such as heart cavities and blood vessels.
Minimally invasive percutaneous surgery, commonly known as “key-hole” surgery, is a well-known surgical technique wherein surgical devices are inserted into a patient's body through a small aperture cut. For example, it is often preferable to use key-hole surgery in cardiovascular procedures, so as to avoid the substantial discomfort, need for general anesthesia, trauma, high risk of infection, and long recovery time typically associated with conventional surgery.
Key-hole surgery is often used in the treatment of coronary heart disease, in which a coronary artery is partially occluded by a blockage such as an atheroma. For example, in balloon angioplasty, a balloon catheter including a flexible, hollow tube is inserted into an artery, usually near the patient's groin, and is guided through the body to the patient's heart. The heart and the cardiac arteries may be visualised using X-ray fluoroscopy, and the tip of the catheter may be fluorescent so that its position can be determined. The catheter carries an inflatable balloon near its distal tip. The balloon is positioned in or near to the blockage, and then the balloon is inflated so as to widen or dilate the occluded blood vessel to restore blood flow through the coronary artery to the cardiac tissue.
A tubular supporting device (e.g., stent) may be deployed at the site of the blockage to prevent future occlusion (restenosis) or collapse of the blood vessel. The stent may, for example, be an expandable metal mesh tube which is carried on the balloon of the balloon catheter. While on the catheter, the tube has a relatively small diameter in comparison to the diameter of the blood vessel. The stent expands when the balloon is inflated, so that the stent pushes against the wall of the blood vessel. The stent is arranged to retain its expanded shape when it reaches its expanded position, for example by plastic deformation or by means of a mechanical locking mechanism, so as to form a resilient scaffold or support in the blood vessel. The support structure (e.g., stent) supports and dilates the wall of the blood vessel to maintain a pathway for blood to flow through the vessel. Self-expanding stents are also available, which are held in a collapsed state by a suitably adapted catheter for transport through the artery and which adopt an expanded state when deployed at the site of the blockage. The catheter may, for example, include a retaining sleeve which retains the stent in a compressed or unexpanded state. Upon removal or withdrawal of the sleeve from the stent, the stent expands to support and dilate the wall of the blood vessel.
In acute cases of coronary heart disease, where a coronary artery is severely or completely occluded, angioplasty may not be suitable. Instead, coronary bypass surgery may be required. Bypass surgery is an open-chest or open-heart procedure, and typically involves grafting a piece of healthy blood vessel onto the coronary artery so as to bypass the blockage and restore blood flow to the coronary tissue. The healthy blood vessel is usually a vein harvested from the patient's leg or arm during the course of the bypass operation. To perform the procedure, the patient's heart must be exposed by opening the chest, separating the breastbone, and cutting the pericardium surrounding the heart, resulting in significant surgical trauma.
Certain patients are unsuitable as candidates for conventional coronary bypass surgery, due low expectation of recovery or high risk from the significant trauma due to surgery, high risk of infection, absence of healthy vessels to use as bypass grafts, significant co-morbidities, and expected long and complicated recovery time associated with open-chest surgery. For example, factors such as diabetes, age, obesity, and smoking may exclude patients who are in need of treatment.